Worn BB shell thread - how does recutting it help?

[craker]

My bottom bracket was loose last night so I stripped the bike down and tried tightening it - however it wont tighten . I've put another bb in , this one seems to have a better thread and has tightened up however I know the thread in the shell is on the way out.

Is there anything I can do to ensure the current BB stays tight? Threadlock, ptfe tape I suppose.

How does recutting the thread help? (Its an older steel frame btw). If the ridges of the thread have vanished then how does taking more metal away help?

Ta.

[Chris N]

It'll clean up what's left and allow the new cups to screw in more easily.  If loctite or ptfe doesn't work then you can get threadless bbs that don't rely on the frame threads at all.

[Wobbly John]

Some frame-builders will put a layer of braze on and re-cut the threads into that - this would means a re-spray though.

You can get 'tapered cone bottom brackets' for use in frames where the thread is damaged. YST used to do one, but no doubt a forummer with recent experience will be along with a recommendation and where to buy from.

[rafletcher]

It's possible to ream out the BB shell and put in a tubular insert that is then threaded. I know that such inserts can be brazed in (and as WJ says that mean a respray) but it should be possible (technically) to press fit a new sleeve in - I'd give Argos cycles in Bristol a call to tap into their expertise. Especially not press-fit BB's are becoming more common.

The current BB issue is one I'd use PTFE tape for - I'd be worried that relative movement would cause threadlock to fracture.

[wooliferkins]

If it's JIS square taper then Acor do a repair BB for just this.  The "adjustable cup screws onto the main body of the BB and angled cups centre it.

Neil

[craker]

Yeah I've seen these threadless BBs - anyone had any experience of them? I'm concerned that I might have to get the BB Shell faced (how else are the two cups kept parallel?). I suppose once installed properly they're as stiff as a normal one.

[Paul Rainbow]

Saw a Velo Orange one at Bespoked Bristol this year, looked very well made :

http://store.velo-orange.com/index.php/grand-cru-threadless-bottom-brackets.html

Think Fresh Tripe are the UK suppliers though you may be able to buy direct. Some review info here :

http://tsaleh.blogspot.co.uk/2010/01/review-velo-orange-grand-cru-threadless.html

I would recommend facing the BB shell if possible, will ensure a better fit. I have only fitted the old Mavic threadless BBs but you had to use a special tool to face the bb shell on an angle, these look like an easier job all round.

[Hello, I am Bruce]

I've had a YST threadless bottom bracket on my Galaxy for years.  It's pedalled hard up many miles of steep rough roads with heavy luggage without problems.

I took the cranks off after it's first few rides after fitting and give it an extra tighten, but not done anything since.  I didn't use any threadlock on it.  I used two splined bottom bracket tools to fit it (I've seen reports of failure when relying on friction to hold one end when tightening).

Mine was from Spa, who seem to do an own-brand one now (maybe actually the same model).

[Someone will be along in a minute to say that it didn't work for them.]

[andrew_s]

I used to use a Mavic threadless BB, on which the lockrings had a 45° chamfer, and which required that the ends of the BB shell had a matching chamfer. This was rock solid and lasted until riding through floodwater followed by neglect killed it. In practice it isn't absolutely necessary to get the chamfer put on the BB shell - tightening up a few times will develop enough of a chamfer for it to work. This will apply to any other threadless BBs with a similar inward-pointing taper (Stronglight did one too).
Any threadless BB that relies completely on widthways clamping with nothing to resist up/down movement other than the clamping pressure will be vulnerable to movement and consequent loosening.
For cheap, there are (or were) also cartridge BB with nylon press in cups.

Buying now, I'd probably get the Velo Orange expanding version.


For a permanent fix, I had the BB threads in a frame replaced by Argos using the ream and sleeve method mentioned above. This has given no problems in the 15 years or so since.
Other framebuilders may also repair BB threads by either building up with braze and then threading the braze (I personally wouldn't trust this long term), or by cutting a saw slot through the BB shell, squeezeing the slot shut and brazing/welding it, then recutting the threads in the now slighly smaller diameter BB shell.

[frankly frankie]

Any threadless BB that relies completely on widthways clamping with nothing to resist up/down movement other than the clamping pressure will be vulnerable to movement and consequent loosening.

Any external bearings type BB (such as Hollowtech II) would probably work just as well if not better.  You don't have to fit these anything like as tightly as you would a traditional BB, and again it's the widthways clamping (which itself mustn't be over-tight) which holds it all together.

[mrcharly-YHT]

I had a severely distorted BB shell. Two frame builders said it was a remove and replace job. The Prestige/YST BB shell wouldn't work - there was just too much distortion.
 
I applied Epoxy putty and (over hours) sanded it back until the Prestige shell would only fit in with thumps from a lump of wood. Then applied epoxy to the BB, fitted and tightened it. The BB has never moved.

This is a desperation step tho, because removing that BB is going to damage the frame. The BB bearings are going now, probably wear accelerated by the forced fitting.

Don't bother with PTFE - it's far too soft and the BB will just move and cause further damage to the shell. You could try a viscous Epoxy on the threads and then screw in your existing BB, but it might make the BB impossible to remove.

[LittleWheelsandBig]

If you heat up the epoxy, it'll come out. The degradation temperature is generally surprisingly low.

[aidan.f]

Epoxy works  well, If  you don't  degrease too thoroughly it  will come  apart  as  well.

[craker]

Sorry, you've lost me with this epoxy fix.

Is something like Araldite a solution? I imagine I'll have to degrease everything first. If I do go the Araldite route is there any removing of the bottom bracket?

Edit - maybe we're looking at http://www.amazon.co.uk/gp/product/B00361819W/ref=pd_lpo_k2_dp_sr_3?pf_rd_p=103612307&pf_rd_s=lpo-top-stripe&pf_rd_t=201&pf_rd_i=B003BPX9EK&pf_rd_m=A3P5ROKL5A1OLE&pf_rd_r=0P0EHRZ45Q58AS2J08FN

[Biggsy]

Araldite is a make of epoxy.  You can find cheaper brands that are just as good.  I use Wilkos for various jobs.

There are lots of types of epoxy, including some designed to bond especially well to metal - which you might or might not want for a BB, depending on how bad it is.

[Biggsy]

Epoxy resin (eg Araldite), and fitting the BB before it's set, is more usually recommended than epoxy putty, but I don't know what's best.  You have to remove the BB in any case.

[craker]

You have to remove the BB in any case.

Yeah, I think I meant will it ever come out again.